JPH09166185A - Small-sized reduction gear having two deceleration stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high reduction gear radio in the state where the whole dimension is minimized by setting the outer form of teeth in the center part smaller than the tooth bottom circle of a first gear, and forming a pinion by the center part. SOLUTION: Two half hears 31, 32 are surely fixed in the axial direction and rotating direction to a core 33 by bending the axial tubular end part 36 of the core 33 onto the outer surface of the half bears 31,32 in the inside of a tubular part 34 followed by, for example, swaging. Teeth 41 forming a pinion 4 of second deceleration stage are formed on the core 33 within the free space between the two half bears 31, 32. The outer diameter of the gear 41 is set smaller than the tooth bottom circles of the two half gears 31,32 so that they are never interfered with the screw 22 of a worm screw 2 when the worm screw 2 is engaged with the teeth 35 of the half gears 31, 32. Thus, a torque can be surely transmitted between an output gear 3 of gear/worm screw stage and the input pinion 4 of second deceleration stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction gear having two reduction stages capable of obtaining a high reduction ratio between input and output.

[0002]

2. Description of the Related Art It is known to use a gear / worm system to obtain a high reduction ratio. This reduction ratio directly depends on the number of teeth of the gear, but as the number of teeth increases, the diameter of the gear increases, and thus the size of the entire reduction gear increases. It is known to use speed reduction stages. For example, there is a method of adding another pinion-gear pair and screwing the pinion with a gear of a gear / worm screw system. However, even if the pinion is attached directly to the gear, the lateral dimension of the reduction gear assembly will be large.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reduction gear that can obtain a high reduction gear ratio while minimizing the overall size.

[0004]

According to the present invention, there is provided a first reduction gear stage composed of a gear / worm screw system including a worm screw and a first gear, a second gear and a pinion engaged therewith. A reduction gear having two reduction stages including a configured second reduction stage, two side parts in which a first gear of a gear / worm screw system is axially spaced from each other; A central portion disposed between the two side parts, the two side parts having teeth for engaging the threads of the worm screw, the central part having teeth, the outer diameter of the teeth Provides a reduction gear characterized in that it is smaller than the root circle of the first gear and the central portion constitutes a pinion.

The lateral dimensions of the reduction gear of the present invention do not exceed those required for a gear / worm screw system. Further, since the pinion and the gear forming the second reduction stage are located on the center plane of the gear / worm screw system, the reduction gear is symmetrical with respect to this plane. Therefore, the application to the mechanism driven by the reduction gear is simplified. Also, the drive torque is transmitted to the two parts of the first gear by the worm screw,
Since the resistance torque of the pinion is applied between the two parts, the load on the bearings supporting the first gear and pinion assembly is evenly distributed on both sides. Other features and advantages of the invention will be apparent from the following description which illustrates one example of a reduction gear of the invention.

The reduction gear casing 1 according to the invention comprises two symmetrical parts connected to each other by a clamp rivet 13.
2 composed of 11 and 12 and housed in this casing 1
The first reduction stage includes a worm screw 2 and a helical gear 3, and a second stage including a pinion 4 and a second gear 5.
It consists of steps. The worm screw 2 is arranged in the casing with its axis on the joint surface of the symmetrical parts 11, 12 of the casing. Both ends of the worm screw 2 are inserted into the bearing 14. These bearings 14 also serve as axial stoppers for the worm screw 2. A bore is formed in the casing at a position on the axis of the worm screw 2. A shaft of a drive motor (not shown) is attached to this bore. This shaft is inserted into, for example, a hole 21 having a square cross section formed in the axial portion of the worm screw 2.

The helical gear 3 is composed of two half gears 31, 32 made of, for example, plastic. These half gears 31, 32 are mounted on both sides of a core 33 made of metal, for example, in alignment with one another and at a distance from one another. The two half gears 31, 32 are of the same shape and have on their outer surface an annular portion 34, which extends axially outwardly and which is formed in each of the housing parts 11, 12 with a bore 15. It is guided in a freely rotatable state. These bores 15 serve as bearings for directly supporting the half gears 31, 32, are formed in the boss 16 of the casing, and serve to securely position the gear 3 in the axial direction. Two half gears 31, 32
Helical teeth 35 are formed on the peripheral edge of the. These helical teeth 35 are such that when the two half gears 31, 32 are attached to the core 33, the two helical teeth 35 together screw together with a worm screw like a normal pinion / worm reduction gear. It is designed to form gears.

The two half gears 31, 32 are axially and axially relative to the core 33 by bending, eg swaging, the axial tubular end 36 of the core 33 inside the annular portion 34 onto the outer surface of the half gear. The rotation direction is securely fixed. In the free space between the two half gears 31 and 32, teeth 41 forming the pinion 4 of the second reduction stage are formed in the core. To prevent the worm screw 2 from interfering with the screw 22 of the worm screw 2 when it engages with the tooth 35 of the half gear 31, 32, this tooth
The outer diameter of 41 is smaller than the root circles of the two half gears 31 and 32.

The central portion 37 of the core 33 with the teeth 41 extends axially a distance greater than the distance between the two half gears. The teeth 41 extend over substantially the entire width of the central portion 37, with both ends of the central portion 37 being inserted into a housing 38 having corresponding inner teeth formed in the half gears 31,32. If the semi-gear is made of plastic, the housing and its inner teeth can be easily manufactured by molding. Due to the presence of the inner teeth, the relative positions of the teeth of the two half gears can be reliably positioned, and at the same time the half gear and the core can be reliably rotationally connected, and thus the output gear 3 of the gear / worm screw stage and the second gear
The torque can be reliably transmitted to and from the input pinion 4 of the deceleration stage.

The gear 5 of the second reduction stage has a hub 51 made of plastic on which a metal ring 55 is preferably mounted securely. The metal ring 55 has teeth on the outside which pass between the two half gears 31, 32 and lead to the core 33.
It is screwed with the tooth 41 of. Therefore, the thickness of the metal ring 55 is slightly smaller than the distance between the half gears 31 and 32.

The hub 51 has a central hole 52 with a square cross section or with splines etc. into which the output shaft 53 of the reduction gear with a corresponding cross section is inserted. Since the reduction ratio obtained by the two reduction stages of the reduction gear is large,
Since the torque is considerably large, the metal reinforcing plate 54 having a hole with the same cross section as the hub is embedded in the hub to reinforce the hub and securely transmit the output torque to the output shaft 53. It is preferable to prevent damage to the square center hole 52 or splines. The gear 5 is preferably manufactured by multicolor molding (overmolding) a plastic hub 51 on a ring 55 with a gear and a reinforcing plate 54.

In order to ensure the positioning of the hub in the casing, the bore 17 which functions as a bearing formed in two parts constituting the casing 1 is provided in the same manner as in the mounting method of the gear 3.
Preferably, the axial end 56 of the hub is rotatably mounted on. By making the hub 51, the half gears 31, 32 and the plastic material, the structure of the reduction gear is made as simple as possible, and is excellent between the plastic material used (eg polyamide) and the casing material (eg Zamak Zamak). Utilizing the coefficient of friction eliminates the need for additional bushings or bearings for the gears 3, 5. The invention is particularly applicable to motor drive mechanisms for adjusting motor vehicle seats.

[Brief description of the drawings]

FIG. 1 is a plan view of a reduction gear with a casing opened.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an exploded view showing various parts of the reduction gear.

FIG. 4 is a front view of a gear / worm screw system gear and a member serving as a pinion of a second reduction stage.

[Explanation of symbols]

1 Housing 2 Worm Screw 3 First Gear 4 Pinion 5 Second Gear 15 Bore 22 Threads 31, 32 Half Gear 33 Core 34 Annular Part 36 Axial End 37 Center Part 38 Housing 41 Teeth 51 Hub 54 Reinforcing Plate 55 Metal ring

Claims (9)

[Claims] 1. A first reduction stage composed of a gear / worm screw system including a worm screw (2) and a first gear (3),
A reduction gear having two reduction stages including a second reduction stage composed of a second gear (5) and a pinion (4) engaged with the first gear (3) of a gear / worm screw system. ) Are two side pieces (31, 32) axially spaced from each other,
Central part located between these two side parts (31, 32)
(37), the two side parts (31, 32) have teeth (35) that mesh with the threads (22) of the worm screw, and the central part (37) has teeth (41). However, the outer diameter of the tooth (41) is smaller than the root circle of the first gear (3), and the central portion (37) constitutes a pinion (4). 2. A core in which the first gear (3) has teeth (41).
Reduction gear according to claim 1, constituted by two half gears (31, 32) aligned with (33). 3. Reduction gear according to claim 2, wherein the two half gears (31, 32) are made of a plastic material. 4. An annular portion (34) is provided on the outer surface of the two half gears (31, 32), the annular portion (34) extending axially outward and forming a bore (15) in the casing. ) Is rotatably guided and these bores (15) serve as bearings for the semi-gear (31, 32). 5. A central portion (37) of a core (33) having teeth (41)
A housing with a corresponding axial inner tooth formed on the semi-gear (31, 32) at both ends of the central part (37) whose axial width is greater than the distance between the two semi-gears (31, 32). 38) The reduction gear according to claim 2, which is inserted into the gear. 6. The reduction gear according to claim 2, wherein the axial end portion (36) of the core (33) is bent to fix the two half gears (31, 32) in the axial direction of the core (33). . 7. The second gear (5) has a hub (51), which is fixed to a metal ring (55), the metal ring (55) having external teeth. , This outer tooth has two half gears
The reduction gear according to claim 2, wherein the reduction gear is screwed with the teeth (41) of the core (33) through the gaps (31, 32). 8. A reduction gear according to claim 7, wherein the hub (51) is made of a plastic material. 9. The metal reinforcing plate (54) having a bore of the same cross section as the hub (51) is embedded in the hub (51).
Reduction gear described in.